Brush for the supply of electric current



July '15, 1930. c. KUHNEL 1,770,617

BRUSH FOR THE SUPPLY OF ELECTRIC CURRENT Filed Nov. 25, 1928 PatentedJuly 15, 1930 UNITED STATES cm x'ommn, or nnnmn-cnannorrnivnune,GERMANY, nssrenon 'ro smmms- SCHUCKERTWERKE AKTIENGESELLSCHAFT, 0FBERLIN-'SIEMENSSTADT, GERMANY,

A CORPORATION or GERMANY BRUSH FOR THE SUPPLY OF ELECTRIC CURRENTApplication filed November 23, 1928, Serial No. 321,396, and in GermanyNovember 25, 1927.

My invention relates to brushes for the supply of electric current, moreparticularly to commutators of electrical machines.

In universal and commutator motors, particularly those of small sizes,the disadvantage exists that the commutator brushes serving as currentsupply members become worn in course of time and are not exchanged ingood time owing to insuflicient attention. The result is, that the wornbrush takes up an oblique position in the holder or that it is evencompletely-worn out and that ultimately the spring or wire helixpressing on the brush slides itself upon the commutator and damages itbadly. It may even happen that the local temperature rises become sohigh, that after a time the commutator fuses or the armature is burnedout. This drawback is particularly noticeable in motors for domesticmachines, such as vacuum cleaners, floor polishers, pans, kitchenmachines, washing machines or the like, since these machines are handledby unskilled operators, who only notice the wear of the brushes afterthe mo-' tor has sufiered damage. The object of my invention is toeliminate this drawback.

According to my invention the current supply brushes for the commutatorsof electrical machines are so designed, that when the brushes have wornto a certain extent vapors, easily noticeable by the eye and the noseare developed, which call the attention of the operator to the fact,that it is time to exchange the brushes. The action of these vapors maybe so powerful that the attendant cannot possibly overlook the fact thatit is necessary to exchange the brushes.

To attain this result the medium developing the vapors may, forinstance, be placed into a cavity at the extremity of the brush. Thisterminal portion of the brush may, however, equally well be impregnatedor saturated with a medium or substance, which develops the vapors whenthe brush is worn down to that portion. As vapor developing medium amixture of artificial muskand a priming substance consisting of sulphideof antimony, red phosphorus and potassium nitrate has proved suitable.This medium has the advantage, that it spreads a powerful althoughagreeable smell without doing injury to the commutator or other parts ofthe machine. A mixture composed of this priming substance andpowderedvulcanite likewise shows a good action. It will be understood, however,that other suitable agents may be employed which develop vapors easilynoticeable by the nose or the eye, but harmless to the machine.

An embodiment of my invention is illustrated in the drawing afiixedhereto and forming part of my specification.

Referring to this drawing showing a sectional elevation of the brush andholder, 1 is a carbon brush serving for the supply of the current andwhich is forced against the commutator 3 by a helical spring 2, whichalso leads the current to the brush. The brush 1 is guided in a holder.4. Near its end it is provided with a lateral bore 5 into which thereacting chemical 6 developing the vapors is inserted after which thebore is closed again. When the wear of the carbon has proceeded up tothis point the chemical 6 contained in the bore is evaporated orvaporized by the heat developed by the friction and the current betweenthe commutator 3 and the carbon brush 1.

The current of air sweeping past the motor conveys the vapors thusgenerated into the room and giveswarning of the wear of the brushes bythe odor of the vapor developed. In this Way due notice is given at thecorrect time for renewing the brushes.

Y Various modifications and changes may be made without departing fromthe spirit and the scope of the'invention.

I claim as my invention:

1. A current supply brush, more particu-. larly for the commutators ofelectrical machines, consisting of a brush member including. a portiondeveloping easily noticeable vapors when contacting with the commutatorin operation, when the brush has Worn to that portion.

2. A current supply brush, more particu-' larly for the commutator-s ofelectrical machines, consisting of a brush member having a portionintermediate its ends, impregnated with a vapor developing mediumadapted to give a warning by the vapor developed during the commutatoroperation when the impregnated portion contacts with the commutator.

3. A current supply brush, more particularly for the commutators ofelectrical machines, consisting of a. brush member having a cavityintermediate its ends in which is located a vapor developing chemicaladapted when contacting with the operating commutator to develop a vaporto give a warning when the brush should be exchanged.

4. A current supply brush, more particularly for the commutators ofelectrical machines, consisting of a brush member having a portionintermediate its ends, filled with a mixture of powdered vulcanite and apriming material consisting of sulphide of antimony, red phosphorus andpotassium nitrate, adapted when contacting with the op-. erating.commutator to ive a warning when the brush should be exc anged.

In testimony whereof I aflix mv signature.

CARL KUHNEL.

